1. Field of the Invention
The field of the invention relates to produce packages wrapped with a perforated plastic film, and methods for producing such packages.
2. Brief Description of the Prior Art
Plastic film prepackaging of produce such as blueberries and raspberries which have high water content and/or tender stems must provide a free flow of air through the film to help prevent mold growth. Such produce is often packaged in trays or "tills" made of plastic foam, rigid plastic or molded paper pulp. Films wrapped around such trays generally have poor oxygen transmission rates, and the need for perforating the films when used for such applications has accordingly been recognized.
One approach which has been taken for perforating plastic films has been to randomly place perforating needles around a cylinder press, and apply the cylinder to the film during either the printing operation or the wrapping operation. Such an approach has generally resulted in generally ragged perforations which will cause the film to tear as it is stretched over the tray.
Various other approaches have been taken for packaging produce in a manner that adequate ventilation is provided. U.S. Pat. No. 3,067,039 discloses a package including a cover film including slits. The film is secured to prongs extending from the corners of a produce basket.
A wrapping film for use with produce is disclosed by U.S. Pat. No. 3,097,787. The film is vented by pressing it over a toothed roll. It appears to be designed for use in bag form.
U.S. Pat. No. 3,207,300 discloses a transparent web which is provided with a series of pin holes to permit the escape of entrapped air from a package interior during a shrinking process. The method disclosed is said to be applicable to products in bulk form, such as bananas, or partially prepackaged products such as fruit trays.
U.S. Pat. Nos. 3,040,968, 4,815,603 and 4,886,372 disclose various other packaging assemblies or techniques which allow the ventilation of food products.